By Sarah Toyne BBC News Online personal finance reporter

Some people are in debt because of delays

Some of those claiming the new tax credits have received letters in error from the Inland Revenue, terminating their payments before they have even begun, BBC News Online has learned.

It is the latest bungle to hit the introduction of the new tax credit system, which affects nine in 10 families and was introduced in April.

A number of BBC News Online readers said they had received the letters - which say their payments have been stopped, even though they have not received any payments - in the last few days.

The awards notices also incorrectly say the addressees have no qualifying children, their awards are "0.00" - and they will have to appeal.

The government says there are problems with a tiny minority of cases, which they are dealing with, but apologised for any upset it had caused.

People affected

Shancar Cumaraswamy, a systems engineer from Ipswich, and his wife Slojana both received letters on Friday morning.

The new tax credits computer system is not yet performing as well as we would like Inland Revenue spokesman

Mr Cumaraswamy said his wife was "very distressed" to receive the notice, as they had followed the application procedure correctly.

In the Cumaraswamys' case, they were told: "You have not signed and returned the award notice we issued on 00/00/0000. As a result payment of tax credits has stopped."

People who apply on paper, through the post, are not required to send an additional signature to the Revenue.

The Cumaraswamys have not received an awards notice, and are awaiting their payment, which should amount to about �485 a year.

Wendy Parker from West Yorkshire also received the letter from the Revenue, but she says she has been waiting since 10 April for her first weekly payment.

She was sent her original award notice on 31 March, which said she would receive �66.15 a week.

Mrs Parker who also completed her application by post, and used to received the old-style tax credits, has also received a similar letter.

"It would have been better to have kept paying people through giros and then phased everyone in gradually."

Computer problems

The Public & Commercial Services Union - the Inland Revenue staff union - told BBC News Online that the staff, who were still handling about one million calls a week, felt "beleaguered".

The union, which meets on Monday in Scarborough, said a number of motions would be focusing on the anger about the way tax credits were introduced.

Ian Lawrence of the union's Inland Revenue section said it "applauded" the decision by the government to bring in a new benefits system, but said "inadequate planning and forecasting" were causing big problems.

But his main criticism was levelled at the computer system - the subject of a number of motions at next week's conference.

Mr Lawrence said the computer system had broken down five times in the past fortnight.

"There are serious computer problems. The system has been crashing regularly," Mr Lawrence told BBC News Online.

However, the Revenue initially denied there were any computer problems.

A spokesman told BBC News Online: "There are no problems with computer systems."

Mistakes made

However, in a later statement the Revenue changed tack.

It said: "The new tax credits computer system is not yet performing as well as we would like. We are sorry about that and we are working hard with EDS to improve system performance.

"But the system has already helped make millions of payments to millions of families."

The Revenue also admitted it had made mistakes.

"We do our best to minimise mistakes, spot them and put them right. But given the volume of claims being processed on occasion we do make mistakes in collating the necessary information.

"Where mistakes occur we will investigate and sort out as soon as we can," it added.